KINETIC-MODEL FOR ALCOHOL SYNTHESIS OVER A PROMOTED CU/ZNO/CR2O3 CATALYST

The kinetics of the methanol and higher alcohol syntheses (HAS) have been studied over a K2CO3-promoted Cu/ZnO/Cr2O3 catalyst at 285-degrees-C and feed gas partial pressures in the ranges of 16-49 atm for H-2, 8-65 atm for CO, 0-11 atm for CO2, and 0-5 atm for CH3OH. The methanol synthesis is described by a model based on the assumption that both CO and CO2 are converted to methanol, but on different catalytic sites. The HAS kinetics are described by a model in which carbon incorporation into higher alcohols occurs directly from CO, CO2, and CH3OH. This kinetic scheme is consistent with labeling studies which show that CO and CH3OH incorporate into higher alcohols and with the observed analogies between the effects of CO2 on the methanol synthesis and on the higher alcohol synthesis, which suggest that CO2 also incorporates into higher alcohols. Similarities between the successful kinetic models of methanol and higher alcohol synthesis suggest that CO is converted to both methanol and higher alcohols through common intermediates on one type of catalytic site (possibly at alkali/copper interfaces), while CO2 is converted to methanol and higher alcohols on a different catalytic site (related to the copper component of the catalyst).